Finished off Super Mario Bros 2 about a week ago. So, I decided to try 3 and got to the airship in World 7 last night. After picking it up again today, I finished it off in two hours or so (I didn't say I was good at it). They were both beaten on the SNES, Super Mario All-Stars because I didn't want to use warp zones and finishing either game in one sitting without warp zones would either require a lot more time and/or skill.
The SMB games on NES were very important for the system and even modern gamers have played at least one of them, if not all. Last year I decided to go through the three, but I didn't get very far at first. It took me forever to beat the first one. I ended up getting very lucky on Bowser using a well-timed jump that I didn't even plan. Anyway, they are all iconic and I'm glad to have played through them all.
Personally, my favorite was 2 which surprised me because I never liked it when i was a kid and always preferred 3. However, I love the physics of 2 better than the others. It just feels like I have more control. Also, there are more unique characters (for obvious reasons) to fight, and the final boss was a great fight.